Writing on Twitter, Hu published the address of Gao's prison in Aksu district in the northwestern region of Xinjiang, calling on netizens to send postcards wishing him well at Christmas.

"Christmas is nearly here, and we should send a card to our brother who is imprisoned far away in the desert," Hu wrote, in a Tweet that was widely retweeted among the online activist community.

"Even if Gao never gets to see them, the prison guards will, and that will increase their respect for lawyer Gao," he wrote.

"This could lead to an improvement in his prison conditions," Hu said. "I have experienced this sort of thing myself."

"I was jailed between 2008 and 2011, and people sent me cards at Chinese New Year and on my birthday, including cards drawn by my kid," he said. "They all expressed real feeling, and ... for a while, the electrified fences all melted away."

'Loneliness'

Gao's wife Geng He, who now lives in the United States with the couple's two children, said she supports the campaign.

"Over the New Year period, I hope people will send him cards to reduce his feelings of loneliness," Geng said. "Even if he never gets them, it will make the prison guards respect him more."

"And if anyone can afford it, I hope that they would go and visit him, for example, foreign embassy officials, so we could get some real news of him," she said.

Geng said the family is currently in the process of applying for official approval to visit Gao in prison.

"We will go when we get approval," she said.

The last time Gao received a known family visit was on March 24, when his brother and father-in-law saw him in jail for the first time in two years, allaying concerns that he had died.

The prison meeting offered a ray of hope to Gao's family members as they were concerned about his safety after he had disappeared for lengthy periods and re-emerged to say he had been tortured.

Before the latest jail visit, Gao Zhiyi last saw his brother in April 2010 in the custody of public security officers.

When he traveled to Aksu's Shaya county jail after being informed in December 2011 that Gao was being held there, prison authorities told him that Gao was not allowed visitors and did not want to see his family.

Vulnerable people

Once a prominent lawyer lauded by the ruling Chinese Communist Party, Gao fell foul of the government after he defended some of China's most vulnerable people, including Christians, coal miners, and followers of the banned Falun Gong spiritual movement.

In 2006, authorities arrested Gao and handed him a sentence for “inciting subversion” that was later suspended. But over the next five years, Gao repeatedly suffered forced disappearances and torture, Geng said.

In December 2011, China’s official Xinhua news agency said in a terse announcement that Gao had been imprisoned for three years for repeatedly violating his terms of probation.

Hu said he would also be sending cards to other jailed activists during the holiday season, including Sichuan-based writer Tan Zuoren, Guizhou democracy activist Chen Xi, and rights activists Liu Xianbin, Chen Wei, and Cao Haibo, as well as U.S.-based dissident Cheng Guangcheng's nephew, Chen Kegui.

Chen Xi's wife said she is very concerned about her husband's health in jail, where he is serving a 10-year sentence for "incitement to subvert state power."

"He has become very thin, and his leg injury hasn't healed," she said. "He said he hurt it doing regular military drills in prison."

Reported by Xin Yu for RFA's Mandarin service and by Fung Yat-yiu for the Cantonese service. Translated and written in English by Luisetta Mudie.